What is VPD?

Let’s start with the meaning of VPD (stands for Vapor Pressure Deficit). 

Imagine the air around a plant is like a sponge. If the sponge is already full of water, it can’t soak up more. But if it’s dry, it will soak up water quickly. Vapor Pressure Deficit (VPD) is like measuring how thirsty the air is for water.

Why Does This Matter for Plants?

Plants “drink” water through their roots and “breathe out” water through tiny holes in their leaves called stomata. VPD controls how much water plants lose when they breathe.

How VPD Affects Plants

Too High VPD (Dry Air) = Thirsty Plants

• • The air pulls water from the plant too fast.
  • The plant may dry out, get stressed, and stop growing well.

Too Low VPD (Humid Air) = Lazy Plants

• • The air is already full of water, so plants don’t lose much.
  • This slows down how they drink and eat, making them weak.

Just Right VPD = Happy Plants

• • The plant breathes and drinks at a perfect rate.
  • It grows strong, makes food, and stays healthy!

Vapor Pressure Deficit (VPD) is expressed in kilopascal (kPa).

This is because VPD measures the pressure difference between the amount of water vapor in the air and the maximum amount the air can hold at a given temperature.